Abstract

On the Scottish mainland the Great Glen fault (GGF) displaces the Emsian to Frasnian Orcadian Old Red Sandstone (ORS) by only 25–29 km dextrally but net post–ORS dextral offsets in Shetland are much larger (120 km total). Most of the displacement (15–20 km) Permian initiation of the Inner Moray Firth Basin. It probably occurred between Frasnian cessation of Orcadian extension and accompanied transpressional inversion of the Orcadian Basin in the mid-late Carboniferous and/or possibly the late Devonian. Devono-Carboniferous transtension may also have occurred. The earlier history of the GGF includes late Caledonian sinistral motion which must have ceased by the late Emsian.